Biology ETDs

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Control of stomatal aperture is the primary way plants regulate gas exchange in the short-term, but what triggers stomatal responses to water stress is still debated. Chlorophyll-a fluorescence imaging, local leaf temperature, and gas exchange were measured simultaneously following a cut to primary leaf vein of Helianthus annuus to access the effect of local leaf xylem cavitation on leaf function. The treatment was repeated under 3 different vapor pressure deficit (VPD) conditions. Surprisingly, photosynthesis (A) and stomatal conductance (gs) responded inversely immediately following the treatment, indicating that A was not CO2 limited by stomatal closure. Comparisons of fluorescence images and temperature data showed that while both A and gs responded heterogeneously across the measured leaf area, local responses did not correspond spatially or temporally, suggesting that each was the result of a different mechanism and/or was initiated by a separate signal. Since the stomatal response varied with VPD but A did not, it is likely that only gs was ultimately responding to a hydraulic signal. Both A and gs recovered to near steady state levels by 900s after the cut. These results indicate that stomata respond immediately to a sudden hydraulic perturbation and that hydraulic redundancy in sunflower is sufficient to allow quick recovery to local interruption of vascular system. This experiment also provides evidence of transient de-coupling of A and gs following wounding.




stomata, electrical potential, heterogeneous behavior, photosynthesis, hydraulic conductance, hydraulic architecture

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Department Name

UNM Biology Department

First Committee Member (Chair)

Hanson, David

Second Committee Member

Sinsabaugh, Robert